An OLED (Organic Light Emitting Diode) is a light emitting diode using light emission of organic EL (Electroluminescence). An organic EL display using OLEDs is typically thin and light in weight and consumes relatively low power. Further, an organic EL display usually has an excellent response speed, viewing angle and contrast ratio. Therefore, organic EL displays recently attract attention as a next generation flat panel display (FPD).
In an OLED, an organic EL layer is embedded between a cathode and an anode on a substrate. The organic EL layer is formed by laminating a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer and an electron injection layer in that order from the anode side, for example. To form the respective sub-layers (particularly, the hole injection layer, the hole transport layer and the light emitting layer) of the organic EL layer, in one method, liquid droplets of an organic material are discharged onto the substrate by an inkjet method, for example.
The organic material discharged onto the substrate by the inkjet method contains a large amount of solvent. Accordingly, a reduced-pressure drying process for drying the liquid on the substrate in a depressurized state is performed to remove the solvent (see, e.g., Japanese Patent Application Publication Nos. 2014-199806 and 2010-169308, and Japanese Patent No. 5701782).
More specifically, a drying apparatus disclosed in Japanese Patent Application Publication No. 2014-199806 includes: an evacuable processing chamber; a mounting table for supporting a substrate in the processing chamber; and a solvent collecting unit, facing the substrate supported on the mounting table, for collecting solvent volatilized from an organic material film on the substrate.
The solvent collecting unit of the drying apparatus disclosed in Japanese Patent Application Publication No. 2014-199806 has a metallic collecting plate disposed substantially in parallel with a surface of the substrate. A through-hole is formed in the collecting plate. Further, the drying apparatus disclosed in Japanese Patent Application Publication No. 2014-199806 includes a solvent separation device for separating the solvent collected by the collecting plate from the collecting plate by vaporizing the solvent after the drying process. The drying apparatus disclosed in Japanese Patent Application Publication No. 2014-199806 further includes a temperature control device having a peltier element or the like, for controlling a temperature of the collecting plate.
In a drying apparatus disclosed in Japanese Patent Application Publication No. 2010-169308, a porous adsorption member for adsorbing a solvent in solution evaporated during drying is disposed to face a substrate. Further, Japanese Patent Application Publication No. 2010-169308 discloses therein another drying apparatus for drying the adsorption member, in addition to the drying apparatus for adsorbing and drying the solvent in the solution on the substrate. In this drying apparatus, a temperature control unit is provided at a mounting table for mounting the adsorption member.
To shorten the treatment time in the drying apparatus which includes the time for separating the solvent collected by and adsorbed onto the solvent collecting unit, it is important to improve the efficiency of collecting the solvent in the solvent collecting unit or improve the efficiency of vaporizing the solvent from the solvent collecting unit.
However, the drying apparatus disclosed in Japanese Patent Application Publication No. 2014-199806 has a complicated configuration as it uses a temperature control unit for cooling or heating the collecting plate to improve the efficiency of collecting the solvent in the solvent collecting unit, i.e., the collecting plate, or the efficiency of vaporizing the solvent from the collecting plate.
The apparatus disclosed in Japanese Patent Application Publication No. 2010-169308 also has a complicated configuration because the temperature control unit is provided at the mounting table for mounting the substrate to facilitate the vaporization of the solvent from the solvent collecting unit, i.e., the adsorption unit. In addition, another drying apparatus for drying the adsorption member, which is different from the drying apparatus for drying the substrate, is used in the technique disclosed in Japanese Patent Application Publication No. 2010-169308.
Japanese Patent No. 5701782 does not disclose any information thereon.